FIELD OF THE INVENTION
[0001] This invention relates in general to wireless communications, and more particularly
to a system and method for accommodating mobile station synchronization to neighbor
cells by providing an extended search window allowing the mobile station to receive
neighbor cells in an efficient manner.
BACKGROUND OF THE INVENTION
[0002] In recent years, the utilization of wireless communication systems for communicating
telephonically has achieved astonishing popularity. Conventional, voice communications
as well as data communications can be effected telephonically through the use of such
wireless communication systems.
[0003] In a wireless communication system, the communication channel formed between a sending
and a receiving station is a radio channel, operating in a portion of the electromagnetic
spectrum. A wire line connection is not required to effectuate the communication of
a communication signal between the sending and receiving stations. Thus, communication
via a wireless communication system is possible at locations to which formation of
a wire line connection would be impossible or otherwise impractical.
[0004] Cellular communication systems have been implemented using various communication
schemes. Cellular communication systems have been developed which utilize, for example,
FDMA (frequency-division, multiple-access), TDMA (time-division, multiple-access),
and CDMA (code-division, multiple-access) techniques, as well as various combinations
of such techniques. A cellular communication system includes network infrastructure
including a number of separated base transceiver stations, formed of fixed-site radio
transceivers. Users communicate with the infrastructure of a cellular communication
network through the use of a radio telephone or other communicator, typically referred
to as a mobile station. The mobile station receives downlink signals on a forward
link and transmits uplink signals on a reverse link. In this manner, bidirectional
communications are provided between the infrastructure of the cellular communication
network and the mobile station.
[0005] For the successful operation of a cellular communication system, synchronization
is required between mobile stations and the base transceiver station. Such synchronization
generally comes in two forms, including frequency synchronization and time synchronization
of the frames and bits. Frequency synchronization is needed in order to ensure that
the mobile station is synchronized to the carrier frequency of the BTS. Bit and frame
synchronization provides adjustment of the propagation time differences of signals
from different mobile stations so that transmitted "bursts" are received synchronously
with the time slots of the base transceiver station, and so bursts in adjacent time
slots do not overlap. Bit and frame synchronization is also required for the frame
structure due to a higher-level superimposed frame structure for mapping logical signaling
channels onto a physical channel.
[0006] Furthermore, when a mobile terminal is operating in a cellular communication system,
it has to be synchronized to neighboring cells. In order to do this, the mobile station
attempts to receive synchronization channels such as Frequency Correction Channels
(FCCH) and Synchronization Channels (SCH) of the neighboring cells at certain intervals.
On traffic channels, most of the TDMA frames are used for transferring data or speech,
arid limited available frames exist in which such synchronization information may
be received. Partial searches can be performed at different frames to collectively
provide the desired search result. However, within any given available frame, the
number of time slots available are also limited, which can further spread out the
searching operation unless enough consecutive times slots can be made available to
account for all of the possible places in time that a synchronization signal such
as an FCCH can present itself.
[0007] With the introduction of higher-level multislot classes, the consecutive time slots
associated with a frame and available for receiving neighboring cell synchronization
information becomes prohibitively limited. In many cases, there are not enough time
slots to cover the range of times in which an FCCH or other synchronization signal
can be presented, and the receipt of FCCH information must carry over to subsequent
frames.' This can cause significant delays and adversely affect communication throughput.
[0008] One prior art manner that addresses this is described in
3GPP TS 05.08, V8.14.0 (2002-04), "3rd Generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; Radio Subsystem Link
Control" (Release 1999). This specification indicates that the MS may skip receive
operations for neighbor reception purposes. This results in the Rx operation after
the idle frame being skipped to provide the requisite time slots for receiving the
FCCH and SCH information. While this may not be necessary for unidirectional downlink
data transfer (e.g., where sufficient downlink time slots are allocated), unnecessary
breaks in the downlink and/or uplink data transfer can occur when skipping Rx operations
during unidirectional uplink and bidirectional uplink/downlink data transfer. When
using Uplink State Flag (USF), for example, for allocation of uplink resources, this
decreases throughput for both downlink and uplink data transfers, since a permission
to send uplink data is received in a downlink data block. By skipping Rx operations
in the downlink direction, this permission to send uplink data may be missed, causing
further delays. This problem is exacerbated when extended dynamic allocation or USF
granularity (or both) are used, since one Rx block may provide permission to send
multiple Tx blocks.
[0009] United States patent application number
US 2002/006119 A1 discloses a method for defining measurement gaps and a wireless telecommunications
system comprising at least one base station and at least one wireless terminal.
[0010] European patent application publication number
EP 1,246,493 A2 discloses a radio communication system in which information of a unit length is constituted
with a plurality of frames as a set and the information is transmitted/received between
a base station (101) and a mobile station (103).
[0011] European patent application publication number
EP 1,184,992 A2 discloses a spread spectrum communication device that, in a compressed mode, interleaves
bit units across multiple frames using an interleaver.
[0013] Accordingly, there is a need in the communications industry for a manner of receiving
neighbor cell synchronization information that minimizes the impact of widening the
associated search window. The present invention fulfills these and other needs, and
offers other advantages over the prior art.
SUMMARY OF THE INVENTION
[0014] The present invention is defined by the appended independent claims. Certain more
specific aspects of the invention are defined by the dependent claims.
[0015] To overcome limitations in the prior art described above, and to overcome other limitations
that will become apparent upon reading and understanding the present specification,
the present invention discloses a system, apparatus and method for accommodating mobile
station synchronization to neighbor cells by providing an extended search window allowing
the mobile station to efficiently receive neighbor cells. One or more transmit (Tx)
time slots are skipped in an available frame adjacent to a block of time slots available
for receiving neighbor synchronization information. In this manner, the search window
for receiving such synchronization information can be expanded, without the negative
consequences associated with prior art synchronization methodologies.
[0016] In accordance with one embodiment of the invention, a method is provided for accommodating
mobile station synchronization to one or more neighbor cells in a mobile communication
system. The mobile communication system includes base transceiver stations (BTS) each
defining a cell, and at least one mobile station (MS) capable of communicating with
at least one BTS. The method includes utilizing at least one available frame as a
search window in an uplink data transfer multiframe for receiving neighboring cell
synchronization information. At least one transmit time slot in a frame adjacent to
the available frame in the uplink data transfer multiframe is surrendered or "skipped"
to extend the search window. The neighboring cell synchronization information is then
received in the extended search window.
[0017] The following describes various particular embodiments of such a method. For example,
in accordance with one particular embodiment of such a method, surrendering at least
one transmit time slot in a frame adjacent to the available frame involves surrendering
at least one transmit time slot in a frame immediately preceding the available frame.
In a more particular embodiment, this may involve surrendering at least one transmit
time slot from the immediately preceding frame that is closest to the available frame
to provide contiguous time slots in the extended search window. In another particular
embodiment, the method includes maintaining an end boundary of the available frame
to prevent disturbing a successive frame contiguous with the available frame. Another
particular embodiment involves surrendering as many transmit time slots as necessary
to provide the extended search window at a size capable of accommodating all of the
neighboring cell synchronization information, and in other embodiments receive slots
may also be surrendered in the frame adjacent to the available frame and opposite
the frame in which the at least one transmit time slot was surrendered, in order to
further extend the search window. In still other particular embodiments, the neighboring
cell synchronization information includes a Frequency Correction Burst (FB) associated
with a Frequency Correction Channel (FCCH) and/or a Synchronization Burst (SB) associated
with a Synchronization Channel (SCH). In one particular embodiment, utilizing the
available frame(s) as a search window involves utilizing at least one defined Idle
Frame in the uplink data transfer multiframe. Another particular embodiment involves
utilizing any one or more frames in the uplink data transfer multiframe having a plurality
of contiguous available time slots. In other particular embodiments, the MS is associated
with an MS multislot class that accommodates fewer consecutive available time slots
than are available in the search window prior to extension, where surrendering the
transmit time slot(s) may involve surrendering a number of transmit time slots required
to accommodate the MS multislot class. In one particular embodiment, this may involve
surrendering a number of transmit time slots required to provide ten consecutive time
slots, inclusive of the time necessary for MS radio frequency circuitry to change
between a data transfer channel and a synchronization channel. One particular embodiment
of such a method involves at least partially synchronizing the MS with a neighboring
cell corresponding to the synchronization information retrieved via the extended search
window, and another embodiment involves repeating a search for the neighboring cell
synchronization information in a plurality of the available frames to facilitate the
receiving of the neighboring cell synchronization information in the extended search
window of at least one of the plurality of available frames. The synchronization information
in one embodiment includes a Frequency Correction Burst (FB) associated with a Frequency
Correction Channel (FCCH), where the method further includes determining a location
of a Synchronization Channel (SCH) based on a location of the FCCH and receiving the
SCH in an available frame at least one multiframe after the FCCH using a timing offset
relative to a timing offset of the FCCH. The MS of one embodiment may be of a type
in which transmit and receive operations are not simultaneously performed, such as
a type-1 MS.
[0018] In accordance with another embodiment of the invention, a Mobile Station (MS) is
provided, where the MS is operable in a wireless network having a plurality of cells
each defined by a Base Transceiver Station (BTS). The MS includes a transceiver to
communicate with a plurality of neighboring BTSs to receive synchronization channels
transmitted by the neighboring BTSs. The MS also includes a processing module configured
to extend a search window in an uplink data transfer multiframe by sacrificing one
or more transmit time slots in a frame of the uplink data transfer multiframe adjacent
to an available frame where receipt of synchronization channels are expected.
[0019] In accordance with another embodiment of the invention, a system is provided for
synchronizing communications in a mobile communication system. The system includes
a number of cells each defined by a Base Transceiver Station (BTS), and at least one
Mobile Station (MS) for communicating with some of the BTSs neighboring the cell in
which the MS is currently operating. The MS includes a transceiver to communicate
with the plurality of the neighboring BTSs to receive synchronization channels transmitted
by the neighboring BTSs, and further includes a processing module configured to extend
a search window in an uplink data transfer multiframe by surrendering one or more
transmit time slots in a frame of the uplink data transfer multiframe adjacent to
an available frame where receipt of synchronization channels are expected.
[0020] In accordance with another embodiment of the invention, a computer-readable medium
is provided which includes stored instructions that are executable by a computer system
for accommodating mobile station synchronization to one or more neighbor cells in
a mobile communication system. The mobile communication system includes base transceiver
stations (BTS) each defining a cell, and at least one mobile station (MS) capable
of communicating with at least one BTS. The instructions stored on the computer-readable
medium performs steps including utilizing at least one available frame as a search
window in an uplink data transfer multiframe for receiving neighboring cell synchronization
information, surrendering at least one transmit time slot in a frame adjacent to the
available frame in the uplink data transfer multiframe to extend the search window,
and receiving the neighboring cell synchronization information in the extended search
window.
[0021] These and various other advantages and features of novelty which characterize the
invention are pointed out with particularity in the claims annexed hereto and form
a part hereof. However, for a better understanding of the invention, its advantages,
and the objects obtained by its use, reference should be made to the drawings which
form a further part hereof, and to accompanying descriptive matter, in which there
are illustrated and described specific examples of a system, apparatus, and method
in accordance with the invention
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention is described in connection with the embodiments illustrated in the
following diagrams.
FIG. 1 illustrates some general aspects of a GSM/GPRS network environment in which
the principles of the present invention may be utilized;
FIG. 2 illustrates a representative multiframe hierarchy in which search windows may
be manipulated in accordance with the present invention;
FIG. 3, which illustrates a representative 52-multiframe relationship between the
monitoring MS TCH and a neighbor cell BCCH;
FIG. 4 illustrates an example frame portion for an MSC-6 (3+1) configuration;
FIG. 5 illustrates an example frame portion for an MSC-10 or MSC-11 (4+1) configuration;
FIG. 6 illustrates an example frame portion for an MSC-12 (1+4) configuration;
FIG. 7 illustrates an example frame portion for an MSC-12 (1+4) configuration implementing
the principles of the present invention;
FIG. 8 is a flow diagram illustrating one embodiment for monitoring neighbor cell
synchronization channels using a contiguous time slot search window in accordance
with the principles of the present invention;
FIG. 9 is a flow diagram illustrating an embodiment for monitoring neighbor cell FCCHs
using a contiguous time slot search window in accordance with the principles of the
present invention; and
FIG. 10 illustrates a representative mobile station computing system capable of carrying
out operations in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] In the following description of the exemplary embodiment, reference is made to the
accompanying drawings which form a part hereof, and in which is shown by way of illustration
various manners in which the invention may be practiced. It is to be understood that
other embodiments may be utilized, as structural and operational changes may be made
without departing from the scope of the present invention.
[0024] Generally, the present invention provides a system and method for accommodating mobile
station synchronization to neighbor cells by providing an extended, search window
allowing the mobile station to receive neighbor cells in an efficient manner. One
or more Tx slots, in the radio block period adjacent to an idle frame used to receive
neighbor synchronization information, are skipped in order to allow expansion of the
search window. By expanding the search window in this fashion, other time slot operations
such as Rx operations need not be disrupted which can otherwise cause substantial
inefficiencies.
[0025] The present invention is applicable in any type of mobile communication systems/networks
where synchronization to neighboring cells may be required. In order to facilitate
an understanding of the invention, the present invention is described in terms of
a GSM/GPRS network. However, those skilled in the art will readily appreciate from
the description provided herein that the present invention is equally applicable to
analogous networking environments. FIG. 1 illustrates some general aspects of a GSM/GPRS
network environment 100 in which the principles of the present invention may be utilized.
[0026] Global System for Mobile communications (GSM) is a digital cellular communications
system serving as a Public Land Mobile Network (PLMN), where multiple providers may
set up mobile networks following the GSM standard. GSM is capable of providing both
voice and data services. A GSM (or analogous) network 100 typically includes components
such as Mobile Stations (MS) 102, Base Transceiver Stations (BTS) 104, Mobile Switching
Center (MSC) 106, etc. A GSM network may be viewed as a collection of various subsystems,
including the Radio Subsystem (RSS) which covers radio aspects, Network and Switching
Subsystem (NSS) which manages functions such as call forwarding, handover and switching,
and the Operation Subsystem (OSS) that manages the network. Various aspects of the
RSS is described in greater detail below.
[0027] One or more MSs 102 communicate with the BTS 104 via an air interface. The BTS 104
is a component of a wireless network access infrastructure that terminates, the air
interface over which subscriber traffic is communicated to and from the MS 102. The
Base Station Controller (BSC) 108 is a switching module that provides, among other
things, handoff functions, and controls power levels in each BTS 104 of the Base Station
System (BSS) 110. The BSC 108 controls the interface between the Mobile Switching
Center (MSC) 106 and BTS 104 in a GSM mobile wireless network, and thus controls one
or more BTSs in the call set-up functions, signaling, and in the use of radio channels.
[0028] A General Packet Radio System (GPRS) mobile communications network 112 is a packet-switched
service for GSM that mirrors the Internet model and enables seamless transition towards
3G (third generation) networks. GPRS thus provides actual packet radio access for
mobile GSM and time-division multiple access (TDMA) users, and is ideal for Wireless
Application Protocol (WAP) services. The BTS 104 also controls the interface between
the Serving GPRS Support Node (SGSN) 114 and the BTS 104 in a GPRS network 112. Other
BTS, BSC, and SGSN components may also be associated with the network system, as depicted
by BTS 116 and BSC 118 of BSS 120, and SGSN 122.
[0029] The MSC module 106 generally includes the MSC, Visiting Location Register (VLR) 124,
and Home Location Register (HLR) 126. The MSC 106 performs a variety of functions,
including providing telephony switching services and controlling calls between telephone
and data systems, switching voice traffic from the wireless network to the landline
network if the call is a mobile-to-landline call, or alternatively switching to another
MSC if the call is a mobile-to-mobile call. The MSC 106 also provides the mobility
functions for the network, and serves as the hub for multiple BTSs. Generally, it
is the MSC 106 that provides mobility management for subscribers, in order to register
subscribers, and authenticate and authorize services and access for subscribers. In
GSM systems, some of the functionality of the MSC 106 may be distributed to the BSC
108, while in other systems such as TDMA systems, the BSC 108 functions are often
integrated with the MSC 106.
[0030] Associated with the MSC 106 is the HLR 126 and VLR 124. The HLR 126 is a database
that stores information about subscribers in the mobile network, and is maintained
by one or more service providers for their respective subscribers. The MSC 106 uses
the information stored in the HLR 126 to authenticate and register the subscriber
by storing permanent subscriber information including the service profile, the current
location of mobile stations, and activity status of the mobile user. The VLR 124 is
a database that may be maintained by the MSC 106 to keep track of all the visiting
mobile stations within a mobile telephony system.
[0031] The Serving GPRS Support Nodes (SGSN) 114, 122 serve GPRS mobile by sending or receiving
packets via a respective BSS 110, 120, and more particularly via the BSC 108, 118
in the context of GSM systems. The SGSN is responsible for the delivery of data packets
to and from the mobile stations within its service area, and performs packet routing
and transfer, mobility management, logical link management, authentication, charging
functions, etc. In the exemplary GPRS embodiment shown in FIG. 1, the location register
of the SGSN 114 stores location information such as the current cell and VLR associated
with the MS 102, as well as user profiles such as the International Mobile Subscriber
Identity Number (IMSI) of all GPRS users registered with this SGSN. Another network
element introduced in the GPRS context is the Gateway GPRS Support Node (GGSN) 128,
which acts as a gateway between the GPRS network 112 and a packet switched public
data network, such as data network 130. This gateway 128 allows mobile subscribers
to access the public data network 130 or specified private IP networks. The connection
between the GGSN 128 and the public data network is generally enabled through a standard
protocol, such as the Internet Protocol (IP).
[0032] A variety of other network elements may be employed, such as a Short Message Service
Center (SMSC) 132. The SMSC 220 is a network element through which short messages
(
e.g., via Short Messaging Service) may be transmitted, and stored for later transmission
in the event that the message recipient is not reached. The MS 102 may access other
services, such as a Multimedia Messaging Service (MMS) provided via the Multimedia
Message Service Center (MMSC) 134.
[0033] When an MS 102 is operating in a GSM network such as the GSM network environment
100 of FIG. 1, it has to be synchronized to neighbor cells. In order to do this, the
MS 102 attempts to receive certain synchronization channels of the neighboring cells
at certain intervals. A background of the various radio interface channels is provided
below.
[0034] As previously indicated, the RSS includes components such as MSs, and the BSS which
in turn generally includes a plurality of BTSs and a BSC. The BTS includes radio components
such as a transceiver and antenna, while the BSC effects switching between BTSs, manages
network resources, etc. The RSS supports a certain number of logical channels that
fall within two primary categories including the traffic channels (TCH) and the control
channels (CCH). The TCHs are intended to carry data such as encoded speech or user
data in circuit switched mode, while Packet Data TCHs (PDTCH) are intended to carry
user data in packet switched mode. Multiple full rate channels and multiple packet
data TCHs can be allocated to the same MS, which is referred to as multislot configurations
and multislot packet configurations respectively.
[0035] Control channels carry signaling and/or synchronization data. There are currently
four primary control channel categories in GSM systems, including broadcast, common,
dedicated, and CTS control channels. Of particular interest with respect to the present
invention are the broadcast control channels. The broadcast channels include Frequency
Correction Channels (FCCH), Synchronization Channels (SCH), a Broadcast Control Channel
(BCCH) as well as Packet BCCH (PBCCH) channels. As previously indicated, when an MS
102 is operating in a GSM network, it has to be synchronized to neighbor cells. In
order to do this, the MS 102 attempts to receive FCCH and SCH channels of the neighboring
cells at certain intervals. For example, if the selected cell corresponds to the cell
of BTS 104, the neighboring cells in which FCCH and SCH channels are to be received
may include cells 140, 142, etc. Approximate timing for a neighbor cell is available
when FCCH information has been received successfully. The timing and frequency synchronization
can be further improved by a successful SCH reception.
[0036] More particularly, the FCCH carries information for frequency correction of the MS
102, and is essentially the repeated transmission of Frequency correction Bursts (FB).
FBs provide a predetermined number of bits of information, such as one hundred forty-two
bits of information, as well as tail and guard periods. This information is transmitted
periodically from the BTS to notify the MSs of frequency adjustments. The information
transmitted is generally null data, i.e., binary zeros, which corresponds to broadcasting
an unmodulated carrier - a sine wave. Using this information, the MS can identify
the channel. The SCH is also used for synchronization. Synchronization Bursts (SB)
on the SCH transmit information which allows the MS to synchronize time-wise with
the BTS. SBs are structured such that they include data bits and synchronization bits,
which includes a Base Transceiver Station Identity (BSIC) as well as a Reduced TDMA
Frame Number (RFN). The RFN is essentially the running number of the TDMA frame, which
facilitates frame synchronization and allows each MS to be time-synchronized with
the BTS. Repeated broadcasting of SBs is considered the SCH.
[0037] In connection with mapping in time of packet logical channels onto physical channels,
a physical channel allocated to carry packet logical channels is referred to as a
Packet Data Channel (PDCH). PDCHs are generally mapped dynamically onto a 52-frame
multiframe. FIG. 2 illustrates an example of a multiframe 200, which includes fifty-two
frames (0-51). Each TDMA frame 202 generally includes eight time slots (0-7). The
length of a typical FCCH burst (i.e., Frequency Correction Burst; FB) is one time
slot, such as depicted by time slot 204. Three tail bits 206, 208 and one hundred
forty-two data bits 210 are all set to zero in the FB to generate a pure sine wave
(PSW) signal. This general multiframe structure is used by the monitoring MS TCH/PDCH,
as well as by the neighboring cell BCCH. From the neighboring cell point of view,
an FB is periodically transmitted by the BTS on the BCCH carrier. It is these FCCH
or FB bursts that are monitored by an MS when attempting to receive synchronization
channels in an appropriate TCH/PDCH frame 202 from neighbor cells/BTSs.
[0038] The FCCH of neighboring cells occurs every 10
th or every 11
th frame in the 51 TDMA multiframe structure; the last gap before the next 51-multiframe
start is ten frames. In idle mode, the FCCH can be received by a monitoring MS via
a continuous search lasting twelve frames. The continuous search is possible in idle
mode since most of the TDMA frames are free for these operations. The corresponding
SCH is then located in the next TDMA frame having the same timing offset as the FCCH.
On traffic channels, most of the TDMA frames are used for transferring data, fax,
speech, etc., and the only available frames in the 52 TDMA multiframe structure are
the so-called "idle frames" which occur every 26
th TDMA frame. Consequently the MS has to perform the search for FCCH in smaller sections.
In practice, this means that one partial FCCH search should last at least nine consecutive
time slots in order to cover all possible places in the time domain in which the FCCH
information may occur during one TDMA frame. Also, SCH reception requires a nine time
slot-wide reception window to cover all possible timing offsets where SCH burst can
be received.
[0039] This situation is depicted in FIG. 3, which illustrates a representative 52-multiframe
relationship between the monitoring MS TCH 300 and a neighbor cell BCCH 302. Since
the neighbor cell FCCH burst 302 (that the monitoring MS is attempting to receive)
is not synchronized with the cell where the monitoring MS is camped, the FCCH burst
302 may be placed anywhere in the time domain. Thus, during one TDMA frame 304 of
the monitoring MS data channel (
e.g., the "idle frame" from the monitoring MS point of view), the neighbor FCCH burst
302 can begin in any time between 0 ms and 4.615 ms in the case of 156.25-bit, 8-slot
TDMA frames. The length of the FCCH burst is one time slot (4.615/8 ms), so to cover
all possibilities to receive one complete FCCH burst the reception or "search window"
should last at least 9 time slots. For example, if the search window were only 8 slots
wide, only a portion 306 of the FCCH burst 308 of the neighbor cell multiframe 302
would be captured in the search window during the X
TH partial search. The remaining portion 310 of the FCCH burst 312 would be captured
in another idle frame during a subsequent, (X+2)
TH partial search 314. Thus, in order to ensure that the FCCH burst can be captured
without such a temporal division, 9 time slots should be used to accommodate for all
possible times in which the FCCH burst can occur.
[0040] When higher GPRS, High Speed Circuit Switched Data (HSCSD), or other similar services
supporting multislot classes are taken into use, there is a problem of obtaining 9
consecutively available time slots for neighbor FCCH and SCH receive (Rx) operations,
since Rx and transmit (Tx) operations occupy most of the time slots. More particularly,
a practical implementation would require at least ten consecutively available time
slots, since the MS radio frequency (RF) components/circuitry has to change frequency
between the data transfer channel and the channel for the neighboring Rx operation,
which requires a certain switching time for type-1 mobile stations having only a single
RF capability (i.e., no concurrent Rx and Tx operations).
[0041] Whether a particular type-1 mobile may experience problems in this regard depends
on the multislot class of the device as well as the Rx/Tx slot configuration for that
multislot class. Table 1 below representative examples of particular multislot classes:
TABLE 1
MULTISLOT CLASS |
MAXIMUM NUMBER OF SLOTS |
Rx |
Tx |
SUM |
1 |
1 |
1 |
2 |
2 |
2 |
1 |
3 |
... |
|
|
|
6 |
3 |
2 |
4 |
... |
|
|
|
10 |
4 |
2 |
5 |
11 |
4 |
3 |
5 |
12 |
4 |
4 |
5 |
Multislot classes are product-dependent, and determine the maximum data rates that
are achievable in both the uplink and downlink. For example, multislot class 6 (MSC-6)
can include a sum of four slots per frame for data transmission, with up to three
Rx slots and up to two Tx slots. The particular configuration is written in the format
"X+Y", where X represents the quantity of downlink time slots, and Y represents the
quantity of uplink time slots. Thus, a multislot class of MSC-6 (3+1) represents multislot
class 6, with three downlink (Rx) timeslots and one uplink (Tx) timeslot per frame.
[0042] Current 3GPP specifications (i.e., 3GPP TS 05.08) allow, for some multislot configurations,
Rx operations related to data transfer in the downlink direction to be skipped to
provide the requisite search window for neighbor reception purposes. While this may
not be necessary for unidirectional downlink data transfer, unnecessary breaks in
the downlink and/or uplink data transfer can occur when skipping Rx operations during
unidirectional uplink and bidirectional uplink/downlink data transfer. When using
an Uplink State Flag (USF) or other analogous indicator for allocating uplink resources,
this decreases throughput for both downlink and uplink data transfers, since a permission
to send uplink data is received in a downlink data block. More particularly, for each
data channel (PDCH in the case of GPRS service) allocated to the MS, a USF is provided
to the MS. Physical channels for packet switched transmission are only allocated for
a particular MS when the MS sends or receives data packets, and are released after
the transmission. Using this "dynamic allocation" principle, multiple MSs can share
one physical channel. To prevent collisions, the network indicates which channels
are currently available in the downlink. The USF in the header of downlink packets
shows which MS is allowed to use this channel in the uplink. Thus, by skipping Rx
operations in the downlink direction, this permission to send uplink data may be missed,
causing further delays. This problem is exacerbated when extended dynamic allocation
or USF granularity (or both) are used, since one Rx block may provide permission to
send multiple Tx blocks.
[0043] FIGs. 4-7 illustrate these multislot class considerations. FIG. 4 illustrates an
example frame portion 400 for an MSC-6 (3+1) configuration. In this example, a TDMA
frame 402 for the uplink includes three Rx time slots 404 and one Tx time slot 406.
An idle frame 408 is used to receive the FCCH burst. For this configuration, eleven
time slots are available, including two time slots 410, 412 to provide the MS with
the appropriate switching time for its RF circuitry, and nine time slots comprising
the FCCH search window 414 for receiving the FCCH information (also generally referred
to as Neighbor Pure Sine Wave; NPSW). Therefore, with this configuration, there is
no particular problem, as the FCCH search can be performed without having to receive
FCCH information non-contiguously in different idle frames.
[0044] FIG. 5 illustrates an example frame portion 500 for an MSC-10 or MSC-11 (4+1) configuration.
In this example, a TDMA frame 502 for the uplink includes four Rx time slots 504 and
one Tx time slot 506. An idle frame 508 is used to receive the FCCH burst. For this
configuration, ten time slots are available, including two partial time slots 510,
512 to provide the MS with the appropriate switching time for its RF circuitry. This
example assumes that the MS RF circuitry can change frequency in half of a time slot
period (
e.g., 577µs/2). Otherwise, this configuration would pose a problem, as 9 consecutive
available time slots would not be attainable. However, in the example of FIG. 5, nine
time slots are available for the FCCH search window 514 to receive the FCCH information.
[0045] FIG. 6 illustrates an example frame portion 600 for an MSC-12 (1+4) configuration.
In this example, a TDMA frame 602 for the uplink includes one Rx time slot 604 and
four Tx time slots 606. An idle frame 608 is used to receive the FCCH burst. For this
configuration, the originally available search window 610 includes less than nine
available time slots, due to the need for two partial time slots 612, 614 to provide
the MS with the appropriate switching time for its RF circuitry. In order to accommodate
for this, the MS may be allowed to skip Rx operations after the idle frame for neighbor
reception purposes. This results in the Rx operation 616 being skipped to provide
the requisite nine time slots for receiving the FCCH information as shown by the new
search window 618. This decreases throughput for both downlink and uplink data transfers
since the USF field is received in a downlink data block. Where extended dynamic allocation
and/or USF granularity are used, one Rx block may provide permission to send multiple
Tx blocks, and thus the problem may be exacerbated.
[0046] The present invention addresses these problems. Rather than skipping downlink receive
(Rx) operations, the search window is widened by skipping transmit (Tx) operations
for uplink data transfer before the idle frame where FCCH or SCH reception is performed.
The search window may be widened by skipping as many Tx operations as necessary to
obtain the requisite search window width. In this manner, skipping the Rx block after
the idle frame can be avoided, and the network can thus use this block to allocate
resources to the MS(s). Thus, the invention has a positive impact on downlink data
since no downlink operations need to be skipped. Further, this is particularly beneficial
in the context of extended dynamic allocation and/or USF granularity use, where the
network can use the first block to allocate several uplink time slots to the MS. This
way, the receipt of the USF value, for example, in the next period can be effected
from all four bursts comprising a GPRS radio block. As a more particular example,
with MSC-12 when extended dynamic allocation and USF granularity is used, this USF
may grant permission to send up to 16 uplink blocks, and it is more significantly
more efficient to ensure receipt of the permission for sending these multiple uplink
blocks relative to losing a single uplink block. Besides allocating resources to the
MS, the network can use the first Rx block after the idle frame to send a control
or data block which can also contain polling for requesting the mobile stations to
send an uplink control block.
[0047] FIG. 7 illustrates an example frame portion 700 for an MSC-12 (1+4) configuration
implementing the principles of the present invention. In this example, a TDMA frame
702 for the uplink generally includes one Rx time slot 704 and four Tx time slots
706, 708, 710, and 712. An idle frame 714 is used to receive the FCCH burst. The originally
available search window 716 includes less than nine available time slots, due to the
need for two partial time slots 718, 720 to provide the MS with the appropriate switching
time for its RF circuitry. In accordance with the present invention, the Rx operation
722 need not be skipped. Rather, the last Tx slot(s) in the frame 702 prior to the
idle frame 714 is surrendered in order to widen the search window as shown by the
new search window 724. With this widened search window 724, nine contiguous time slots
are available for receiving the FCCH information, without the negative impact associated
with skipping Rx operations 722 after the idle frame 714. It should be noted that
MCS 12 is depicted here for purposes of illustration, but the problem will be significantly
more pronounced for other higher multislot classes for type-1 mobile stations (
e.g., multislot class 30-45) when extended dynamic allocation or similar functionality
is used.
[0048] When this kind of search is repeated in a plurality of successive idle frames, the
neighbor synchronization information shall occur during one of the extended search
windows. For example, in the GSM/GPRS environment, this kind of search is repeated
in thirteen consecutive idle frames, the place for the neighbor FCCH burst will occur
during one of the search windows. This is a consequence of different multiframe structures
between common control channels (
e.g., BCCH) and dedicated/shared channels (
e.g., TCH, PDTCH, etc.). After the FCCH has been detected, the location of the SCH is known,
and it can be received in an idle frame 52 frames after the FCCH using the same timing
offset as detected for the FCCH.
[0049] FIG. 8 is a flow diagram illustrating one embodiment for monitoring neighbor cell
synchronization channels using a contiguous time slot search window in accordance
with the principles of the present invention. An available frame, such as a TDMA idle
frame in a data channel, is identified 800 as a search window in the uplink data transfer
multiframe. The available frame is identified for receiving neighboring cell synchronization
information in the uplink data transfer multiframe. In accordance with the invention,
the search window is extended through sacrificing one or more transmit time slots
in a frame adjacent to the available frame in the uplink data transfer multiframe,
as shown at block 802. For example, in one embodiment of the invention, one or more
transmit time slots in the frame immediately preceding the idle frame are skipped
in order to provide a number of contiguous time slots necessary to ensure that the
neighboring cell synchronization information will be captured, regardless of when
during the extended search window the FCCH is provided by the neighboring cell(s).
Alternatively, transmit frames in a successive frame may be skipped, depending on
the multislot class configuration utilized. For example, in a multislot class and
frame configuration where Tx time slots precede Rx time slots, transmit time slots
in a frame immediately succeeding the idle frame may be skipped. In any case, neighboring
cell synchronization information may then be received 804 in the extended search window.
It is noted, however, that this search may be repeated multiple times (such as in
thirteen consecutive idle frames) to ensure a place for the neighbor FCCH to occur
during one of the search windows, as described above.
[0050] FIG. 9 is a flow diagram illustrating an embodiment for monitoring neighbor cell
FCCHs using a contiguous time slot search window in accordance with the principles
of the present invention. A TDMA idle frame is identified 900 as a search window in
the uplink data transfer multiframe, to receive one or more neighboring cell FCCH
bursts. The search window is extended 902 to ten contiguous time slots in the illustrated
embodiment. This is due to one particular requirement where 9 contiguous time slots
are required to ensure receipt of the entire FCCH within an extended search window,
and where MS RF circuitry change frequency in half of a time slot. Therefore, the
requisite 9 contiguous time slots added to two half time slots results in ten time
slots for the extended search window. It will be appreciated by those skilled in the
art from the teachings herein that the search window may be extended to different
lengths, depending on the length of the received FCCH, the MS RF circuitry speed in
changing frequency, the multislot class utilized, etc.
[0051] In the illustrated embodiment of FIG. 9, the search window is extended 902 by skipping
a corresponding number of transmit time slots in the frame prior to the idle frame
in the uplink data transfer multiframe. For example, where ten contiguous time slots
are required (for FCCH plus MS RF frequency change), and nine contiguous time slots
are available in the original search window, then one Tx time slot will be skipped.
Again, a different number of Tx time slots may be skipped, depending on the length
of the received FCCH, the MS RF circuitry speed in changing frequency, the multislot
class utilized, etc.
[0052] In one embodiment, the search may need to be repeated in a plurality of successive
idle frames, such that the neighbor synchronization information occurs during one
of the extended search windows. For example, in the GSM/GPRS environment, this kind
of search is repeated in thirteen consecutive idle frames, the place for the neighbor
FCCH burst will occur during one of the search windows. This is due to the different
multiframe structures between common control channels (
e.g., BCCH) and dedicated/shared channels (
e.g., TCH, PDTCH, etc.). In such case, it is determined 904 whether the search has been
repeated a particular number of times, such as thirteen times. If not, the next idle
frame 906 is considered, and another search window is identified 900. Otherwise, if
the search has been repeated the particular number of times, the neighboring cell
FCCH burst will be received 908 in one of the extended search windows of the repeated
search.
[0053] The present invention may be used with a variety of types of mobile stations, including
wireless/cellular telephones, personal digital assistants (PDAs), or other wireless
handsets, as well as portable computing devices capable of wireless communication.
The mobile stations utilize computing systems to control and manage the conventional
device activity as well as the functionality provided by the present invention. Hardware,
firmware, software or a combination thereof may be used to perform the various synchronization
search window expansion functions and operations described herein. An example of a
representative mobile station computing system capable of carrying out operations
in accordance with the invention is illustrated in FIG. 10.
[0054] The exemplary mobile station (MS) 1000 suitable for performing the synchronization
search window expansion functions in accordance with the present invention may be
associated with a number of different types of wireless devices. The representative
MS 1000 includes a processing/control unit 1002, such as a microprocessor, reduced
instruction set computer (RISC), or other central processing module. The processing
unit 1002 need not be a single device, and may include one or more processors. For
example, the processing unit may include a master processor and associated slave processors
coupled to communicate with the master processor.
[0055] The processing unit 1002 controls the basic functions of the MS as dictated by programs
available in the program storage/memory 1004. Thus, the processing unit 1002 may execute
the search window expansion functions associated with the present invention. Alternatively,
these search window expansion functions may be implemented in software operable on
the Digital Signal Processor 1006, rather than via the MS processing unit 1002. The
program storage/memory 1004 may include an operating system and program modules 1008
for carrying out standard functions and applications on the MS, as well as functions
associated with the search window expansion functions of the present invention. In
one embodiment of the invention, the program modules 1008 are stored in non-volatile
electrically-erasable, programmable read-only memory (EEPROM), flash ROM, etc. so
that the programs are not lost upon power down of the MS. The program storage may
also include one or more of other types of read-only memory (ROM) and programmable
and/or erasable ROM, random access memory (RAM), subscriber interface module (SIM),
wireless interface module (WIM), smart card, or other removable memory device, etc.
The relevant software for carrying out MS operations in accordance with the present
invention may also be transmitted to the MS 1000 via data signals, such as being downloaded
electronically via one or more networks, such as the Internet and an intermediate
wireless network(s).
[0056] The processor 1002 and/or DSP 1006, under the direction of one or more program modules
1008, performs search window expansion functions associated with the present invention.
For example, in one embodiment of the invention, one or more transmit operations are
skipped in the frame immediately preceding the idle frame. The processor 1002 and/or
DSP 1006 perform such skipping functions under the control of one or more software/firmware
programs associated with program modules 1008. While such functions can alternatively
be performed using discrete hardware, these functions are performed using the processor
1002 and/or DSP 1006 in the illustrated embodiment.
[0057] For performing other standard MS functions, the processor 1002 is also coupled to
user-interface 1010 elements associated with the MS 1000. The user-interface 1010
of the MS may include, for example, a display 1012 such as a liquid crystal display,
a keypad 1014, speaker 1016, and microphone 1018. These and other user-interface components
are coupled to the processor 1002 as is known in the art. The keypad 1014 includes
alpha-numeric keys for performing a variety of functions, including dialing numbers
and executing operations assigned to one or more keys. Other user-interface mechanisms
may be employed, such as voice commands, switches, touch pad/screen, graphical user
interface using a pointing device, trackball, joystick, or any other user interface
mechanism. The keypad 1014 will be different depending on the type of MS 1000 utilized.
[0058] The MS 1000 also includes conventional circuitry for performing wireless transmissions.
The DSP 1006 may be employed to perform a variety of functions, including analog-to-digital
(A/D) conversion, digital-to-analog (D/A) conversion, speech coding/decoding, encryption/decryption,
error detection and correction, bit stream translation, filtering, etc., as well as
the functions associated with the present invention. The transceiver 1020, generally
coupled to an antenna 1022, transmits the outgoing radio signals 1024 and receives
the incoming radio signals 1026 associated with the MS.
[0059] The MS 1000 of FIG. 10 is provided as a representative example of a mobile device
in which the principles of the present invention may be applied. From the description
provided herein, those skilled in the art will appreciate that the present invention
is equally applicable in a variety of other currently known and future mobile devices.
[0060] Using the description provided herein, the invention may be implemented as a machine,
process, or article of manufacture by using standard programming and/or engineering
techniques to produce programming software, firmware, hardware or any combination
thereof. Any resulting program(s), having computer-readable program code, may be embodied
on one or more computer-usable media, such as disks, optical disks, removable memory
devices, semiconductor memories such as RAM, ROM, PROMS, etc. Articles of manufacture
encompassing code to carry out functions associated with the present invention are
intended to encompass a computer program that exists permanently or temporarily on
any computer-usable medium or in any transmitting medium which transmits such a program.
Transmitting mediums include, but are not limited to, transmissions via wireless/radio
wave communication networks, the Internet, intranets, telephone/modem-based network
communication, hard-wired/cabled communication network, satellite communication, and
other stationary or mobile network systems/communication links. From the description
provided herein, those skilled in the art are readily able to combine software created
as described with appropriate general purpose or special purpose computer hardware
to create a synchronization search window expansion system and method in accordance
with the present invention.
[0061] The foregoing description of the exemplary embodiment of the invention has been presented
for the purposes of illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise form disclosed. Many modifications and variations
are possible in light of the above teaching. For example, while the present invention
is largely described in terms of GSM/GPRS, the present invention is equally applicable
to other networks and services having similar characteristics as it pertains to the
receipt of synchronization information from neighboring cells, and those skilled in
the art will appreciate from the description provided herein that the principles of
the present invention are equally applicable to such other networks and/or services.
Thus, it is intended that the scope of the invention be limited not with this detailed
description, but rather determined from the claims appended hereto.
1. A method of accommodating mobile station synchronization to one or more neighbor cells
(140, 142) in a time division multiple access mobile communication system (100), wherein
the mobile communication system (100) includes base transceiver stations, BTS, (104)
each defining a cell (140, 142) and at least one mobile station, MS, (102) capable
of communicating with at least one BTS (104), the method comprising:
utilizing at least one first frame as a search window in an uplink data transfer multiframe
for receiving neighboring cell synchronization information;
skipping at least one transmit time slot in a second frame adjacent to the first frame
in the uplink data transfer multiframe to extend (802) the search window, wherein
the second frame adjacent to the first frame further comprises at least one receive
time slot; and
receiving (804) the neighboring cell synchronization information in the extended search
window.
2. The method of claim 1, wherein skipping at least one transmit time slot in a second
frame adjacent to the first frame comprises skipping at least one transmit time slot
in a second frame immediately preceding the first frame.
3. The method of claim 2, wherein skipping at least one transmit time slot in a second
frame immediately preceding the first frame comprises skipping at least one transmit
time slot from the immediately preceding second frame that is closest to the first
frame to provide contiguous time slots in the extended search window.
4. The method of claim 2, further comprising maintaining an end boundary of the first
frame to prevent disturbing a successive frame contiguous with the first frame.
5. The method of claim 1, wherein skipping at least one transmit time slot comprises
skipping as many transmit time slots as necessary to provide the extended search window
at a size capable of accommodating all of the neighboring cell synchronization information.
6. The method of claim 1, further comprising skipping at least one receive time slot
in a third frame adjacent to the first frame and opposite the second frame in which
the at least one transmit time slot was skipped, to further extend the search window.
7. The method of claim 1, wherein the neighboring cell synchronization information comprises
a Frequency Correction Burst, FB, associated with a Frequency Correction Channel,
FCCH.
8. The method of claim 7, wherein the neighboring cell synchronization information further
comprises at least one Synchronization Burst, SB, associated with a Synchronization
Channel, SCH.
9. The method of claim 7, further comprising receiving at least one Synchronization Burst,
SB, associated with a Synchronization Channel, SCH, after the FCCH has been received.
10. The method of claim 1, wherein utilizing at least one first frame as a search window
comprises utilizing at least one defined Idle Frame in the uplink data transfer multiframe.
11. The method of claim 1, wherein utilizing at least one first frame as a search window
comprises utilizing any one or more frames in the uplink data transfer multiframe
having a plurality of contiguous available time slots.
12. The method of claim 1, wherein the at least one mobile station (102) is associated
with a mobile station multislot class which accommodates fewer consecutive available
time slots than are available in the search window prior to extension.
13. The method of claim 12, wherein skipping at least one transmit time slot comprises
skipping a number of transmit time slots required to accommodate the mobile station
multislot class.
14. The method of claim 13, wherein skipping a number of transmit time slots required
to accommodate the mobile station multislot class comprises skipping a number of transmit
time slots required to provide ten consecutive time slots, inclusive of a time required
for mobile station (102) radio frequency circuitry to change between a data transfer
channel and a synchronization channel.
15. The method of claim 1, further comprising at least partially synchronizing the at
least one mobile station (102) with a neighboring cell (140, 142) corresponding to
the synchronization information received via the extended search window.
16. The method of claim 1, further comprising repeating a search for the neighboring cell
synchronization information in a plurality of the first frames to facilitate the receiving
of the neighboring cell synchronization information in the extended search window
of at least one of the plurality of first frames.
17. The method of claim 16, wherein the synchronization information comprises a Frequency
Correction Burst, FB, associated with a Frequency Correction Channel, FCCH, and further
comprising determining a location of a Synchronization Channel, SCH, based on a location
of the FCCH and receiving the SCH in a first frame at least one multiframe after the
FCCH using a timing offset relative to a timing offset of the FCCH.
18. The method of claim 1, wherein the at least one mobile station (102) comprises a mobile
station type where transmit and receive operations are not simultaneously performed.
19. The method of claim 18, wherein the at least one mobile station (102) type comprises
a type-1 mobile station.
20. An apparatus operable in a time division multiple access wireless network (100) comprising
a plurality of cells (140, 142) each defined by a Base Transceiver Station, BTS, (104),
the apparatus comprising:
a transceiver (1020) configured to communicate with a plurality of neighboring BTSs
(104) to receive synchronization channels transmitted by the neighboring BTSs (104)
utilizing at least one first frame as a search window in an uplink data transfer multiframe;
and
a processor (1002) configured to extend (802) the search window by skipping one or
more transmit time slots in a second frame of the uplink data transfer multiframe
adjacent to said first frame, wherein the second frame adjacent to the first frame
further comprises at least one receive time slot;
wherein the transceiver (1020) is further configured to receive the synchronization
channels transmitted by the neighboring BTSs (104) in the extended search window.
21. The apparatus of claim 20, wherein the processor (1002) comprises a processor device
operating under the direction of one or more program modules (1008) having instructions
to direct the processor device to skip the one or more transmit time slots in the
second frame adjacent to the first frame.
22. The apparatus of claim 20, wherein the processor (1002) comprises a Digital Signal
Processor, DSP, (1006) operating under the direction of one or more program modules
having instructions to direct the DSP (1006) to skip the one or more transmit time
slots in the second frame adjacent to the first frame.
23. The apparatus of claim 20, wherein the first frame comprises a defined Idle Frame
in the uplink data transfer multiframe, and wherein the processor (1002) is configured
to extend (802) the search window by skipping at least one transmit time slot in the
second frame immediately preceding the defined Idle Frame.
24. A time division multiple access system comprising:
(a) a plurality of cells (140, 142) each defined by a Base Transceiver Station, BTS
(104);
(b) at least one mobile station, MS, (102) for communicating with a plurality of the
BTSs (104) neighboring the cell (140, 142) in which the at least one mobile station
(102) is currently operating, wherein each of the at least one mobile station (102)
comprises:
(i) a transceiver (1020) to communicate with the plurality of the neighboring BTSs
(104) to receive synchronization channels transmitted by the neighboring BTSs (104)
utilizing at least one first frame as a search window in an uplink data transfer multiframe;
and
(ii) a processor (1002) configured to extend (802) the search window by skipping one
or more transmit time slots in a second frame of the uplink data transfer multiframe
adjacent to said first frame, wherein the second frame adjacent to the first frame
further comprises at least one receive time slot;
wherein the transceiver (1020) is further configured to receive the synchronization
channels transmitted by the neighboring BTSs (104) in the extended search window.
25. The system of claim 24, wherein the mobile communication system (100) comprises a
GSM network.
26. The system of claim 24, wherein the first frame comprises a defined Idle Frame in
the uplink data transfer multiframe, and wherein the processor (1002) is configured
to extend the search window by skipping at least one transmit time slot in the second
frame immediately preceding the defined Idle Frame.
27. A computer-readable medium having instructions stored thereon which are executable
by a computer system for accommodating mobile station synchronization to one or more
neighbor cells (140, 142) in a time division multiple access mobile communication
system (100), wherein the mobile communication system (100) includes base transceiver
stations, BTS, (104) each defining a cell (140, 142) and at least one mobile station,
MS, capable of communicating with at least one BTS (104), the instructions performing
steps comprising:
utilizing at least one first frame as a search window in an uplink data transfer multiframe
for receiving neighboring cell synchronization information;
skipping at least one transmit time slot in a second frame adjacent to the first frame
in the uplink data transfer multiframe to extend (802) the search window, wherein
the second frame adjacent to the first frame further comprises at least one receive
time slot; and
receiving (804) the neighboring cell synchronization information in the extended search
window.
1. Verfahren zum Aufnehmen einer Synchronisierung einer Mobilstation mit einer oder mehreren
Nachbarzellen (140, 142) in einem Zeitmultiplexvielfachzugriff-Mobilkommunikationssystem
(100), wobei das Mobilkommunikationssystem (100) Basissendeempfängerstationen, BTS,
(104), die jeweils eine Zelle (140, 142) definieren, und mindestens eine Mobilstation,
MS, (102) aufweist, die in der Lage ist, mit mindestens einer BTS (104) zu kommunizieren,
wobei das Verfahren Folgendes umfasst:
Verwenden mindestens eines ersten Rahmens als ein Suchfenster in einem Uplink-Datenübertragungsmehrfachrahmen
zum Empfangen von Nachbarzellen-Synchronisierungsinformationen;
Auslassen mindestens eines Übertragungszeitschlitzes in einem an den ersten Rahmen
im Uplink-Datenübertragungsmehrfachrahmen angrenzenden zweiten Rahmen, um das Suchfenster
zu verlängern (802), wobei der an den ersten Rahmen angrenzende zweite Rahmen ferner
mindestens einen Empfangszeitschlitz umfasst; und
Empfangen (804) der Nachbarzellen-Synchronisierungsinformationen im verlängerten Suchfenster.
2. Verfahren nach Anspruch 1, wobei das Auslassen mindestens eines Übertragungszeitschlitzes
in einem an den ersten Rahmen angrenzenden zweiten Rahmen ein Auslassen mindestens
eines Übertragungszeitschlitzes in einem dem ersten Rahmen unmittelbar vorangehenden
zweiten Rahmen umfasst.
3. Verfahren nach Anspruch 2, wobei das Auslassen mindestens eines Übertragungszeitschlitzes
in einem dem ersten Rahmen unmittelbar vorangehenden zweiten Rahmen ein Auslassen
mindestens eines Übertragungszeitschlitzes aus dem unmittelbar vorangehenden zweiten
Rahmen umfasst, der dem ersten Rahmen am nächsten liegt, um im verlängerten Suchfenster
zusammenhängende Zeitschlitze bereitzustellen.
4. Verfahren nach Anspruch 2, ferner umfassend ein Beibehalten einer Endbegrenzung des
ersten Rahmens, um ein Stören eines mit dem ersten Rahmen zusammenhängenden nachfolgenden
Rahmens zu verhindern.
5. Verfahren nach Anspruch 1, wobei das Auslassen mindestens eines Übertragungszeitschlitzes
ein Auslassen sovieler Übertragungszeitschlitze wie nötig umfasst, um das verlängerte
Suchfenster in einer Größe bereitzustellen, in der es in der Lage ist, die gesamten
Nachbarzellen-Synchronisierungsinformationen aufzunehmen.
6. Verfahren nach Anspruch 1, ferner umfassend ein Auslassen mindestens eines Empfangszeitschlitzes
in einem dritten Rahmen, der an den ersten Rahmen angrenzt und dem zweiten Rahmen,
in dem der mindestens eine Übertragungszeitschlitz ausgelassen wurde, gegenüberliegt,
um das Suchfenster weiter zu verlängern.
7. Verfahren nach Anspruch 1, wobei die Nachbarzellen-Synchronisierungsinformationen
einen einem Frequenzkorrekturkanal, FCCH, zugehörigen Frequenzkorrekturburst, FB,
umfassen.
8. Verfahren nach Anspruch 7, wobei die Nachbarzellen-Synchronisierungsinformationen
ferner mindestens einen einem Synchronisierungskanal, SCH, zugehörigen Synchronisierungsburst,
SB, umfassen.
9. Verfahren nach Anspruch 7, ferner umfassend ein Empfangen mindestens eines einem Synchronisierungskanal,
SCH, zugehörigen Synchronisierungsbursts, SB, nachdem der FCCH empfangen wurde.
10. Verfahren nach Anspruch 1, wobei das Verwenden mindestens eines ersten Rahmens als
ein Suchfenster ein Verwenden mindestens eines definierten unbelegten Rahmens im Uplink-Datenübertragungsmehrfachrahmen
umfasst.
11. Verfahren nach Anspruch 1, wobei das Verwenden mindestens eines ersten Rahmens als
ein Suchfenster ein Verwenden irgend eines oder mehrerer Rahmen im Uplink-Datenübertragungsmehrfachrahmen
mit einer Mehrzahl zusammenhängender verfügbarer Zeitschlitze umfasst.
12. Verfahren nach Anspruch 1, wobei die mindestens eine Mobilstation (102) einer Mobilstations-Multislot-Klasse
angehört, die weniger aufeinanderfolgende verfügbare Zeitschlitze aufnimmt, als vor
der Verlängerung im Suchfenster verfügbar sind.
13. Verfahren nach Anspruch 12, wobei das Auslassen mindestens eines Übertragungszeitschlitzes
ein Auslassen einer zum Aufnehmen der Mobilstations-Multislot-Klasse nötigen Anzahl
an Übertragungszeitschlitzen umfasst.
14. Verfahren nach Anspruch 13, wobei das Auslassen einer zum Aufnehmen der Mobilstations-Multislot-Klasse
nötigen Anzahl an Übertragungszeitschlitzen ein Auslassen einer zum Bereitstellen
von zehn aufeinanderfolgenden Zeitschlitzen nötigen Anzahl an Übertragungszeitschlitzen
umfasst, einschließlich einer von der Hochfrequenzschaltung der Mobilstation (102)
zum Wechseln zwischen einem Datenübertragungskanal und einem Synchronisierungskanal
benötigten Zeit.
15. Verfahren nach Anspruch 1, ferner umfassend ein zumindest teilweises Synchronisieren
der mindestens einen Mobilstation (102) mit einer Nachbarzelle (140, 142), die den
über das verlängerte Suchfenster empfangenen Synchronisierungsinformationen entspricht.
16. Verfahren nach Anspruch 1, ferner umfassend ein Wiederholen einer Suche nach den Nachbarzellen-Synchronisierungsinformationen
in einer Mehrzahl der ersten Rahmen, um das Empfangen der Nachbarzellen-Synchronisierungsinformationen
im verlängerten Suchfenster mindestens eines der Mehrzahl erster Rahmen zu erleichtern.
17. Verfahren nach Anspruch 16, wobei die Synchronisierungsinformationen einen einem Frequenzkorrekturkanal,
FCCH, zugehörigen Frequenzkorrekturburst, FB, umfassen, und ferner umfassend ein Bestimmen
eines Standorts eines Synchronisierungskanals, SCH, auf Grundlage eines Standorts
des FCCH und Empfangen des SCH in einem ersten Rahmen mindestens einen Mehrfachrahmen
nach dem FCCH unter Verwendung eines Timing-Versatzes gegenüber einem Timing-Versatz
des FCCH.
18. Verfahren nach Anspruch 1, wobei die mindestens eine Mobilstation (102) eine Mobilstation
eines Typs umfasst, bei dem Übertragungs- und Empfangsbetrieb nicht gleichzeitig erfolgen.
19. Verfahren nach Anspruch 18, wobei der Typ der mindestens einen Mobilstation (102)
eine Mobilstation des Typs 1 umfasst.
20. Vorrichtung, die in einem Zeitmultiplexvielfachzugriff-Drahtlosnetz (100) betreibbar
ist, das eine Mehrzahl jeweils durch eine Basissendeempfängerstation, BTS, (104) definierter
Zellen (140, 142) umfasst, wobei die Vorrichtung Folgendes umfasst:
einen Sendeempfänger (1020), der dafür konfiguriert ist, mit einer Mehrzahl von Nachbar-BTSs
(104) zu kommunizieren, um unter Verwendung mindestens eines ersten Rahmens als ein
Suchfenster in einem Uplink-Datenübertragungsmehrfachrahmen durch die Nachbar-BTSs
(104) übertragene Synchronisierungskanäle zu empfangen; und
einen Prozessor (1002), der dafür konfiguriert ist, durch Auslassen eines oder mehrerer
Übertragungszeitschlitze in einem an den ersten Rahmen angrenzenden zweiten Rahmen
des Uplink-Datenübertragungsmehrfachrahmens das Suchfenster zu verlängern (802), wobei
der an den ersten Rahmen angrenzende zweite Rahmen ferner mindestens einen Empfangszeitschlitz
umfasst,
wobei der Sendeempfänger (1020) ferner dafür konfiguriert ist, im verlängerten Suchfenster
die durch die Nachbar-BTSs (104) übertragenen Synchronisierungskanäle zu empfangen.
21. Vorrichtung nach Anspruch 20, wobei der Prozessor (1002) eine Prozessoreinrichtung
umfasst, die unter der Anleitung eines oder mehrerer Programmmodule (1008) arbeitet,
die Anweisungen enthalten, um die Prozessoreinrichtung anzuleiten, den einen oder
die mehreren Übertragungszeitsschlitze im an den ersten Rahmen angrenzenden zweiten
Rahmen auszulassen.
22. Vorrichtung nach Anspruch 20, wobei der Prozessor (1002) einen Digitalsignalprozessor,
DSP, (1006), umfasst, der unter der Anleitung eines oder mehrerer Programmmodule arbeitet,
die Anweisungen enthalten, um den DSP (1006) anzuleiten, den einen oder die mehreren
Übertragungszeitschlitze im an den ersten Rahmen angrenzenden zweiten Rahmen auszulassen.
23. Vorrichtung nach Anspruch 20, wobei der erste Rahmen einen definierten unbelegten
Rahmen im Uplink-Datenübertragungsmehrfachrahmen umfasst und wobei der Prozessor (1002)
dafür konfiguriert ist, durch Auslassen mindestens eines dem definierten unbelegten
Rahmen unmittelbar vorangehenden Übertragungszeitschlitzes im zweiten Rahmen das Suchfenster
zu verlängern (802).
24. Zeitmultiplexvielfachzugriff-System, umfassend:
(a) eine Mehrzahl jeweils durch eine Basissendeempfängerstation, BTS (104) definierter
Zellen (140, 142),
(b) mindestens eine Mobilstation, MS, (102) zum Kommunizieren mit einer Mehrzahl der
BTSs (104), die benachbart zu der Zelle (140, 142) liegen, in der die mindestens eine
Mobilstation (102) aktuell in Betrieb ist, wobei jede der mindestens einen Mobilstation
(102) Folgendes umfasst:
(i) einen Sendeempfänger (1020), um mit der Mehrzahl der Nachbar-BTSs (104) zu kommunizieren,
um unter Verwendung mindestens eines ersten Rahmens als ein Suchfenster in einem Uplink-Datenübertragungsmehrfachrahmen
durch die Nachbar-BTSs (104) übertragene Synchronisierungskanäle zu empfangen; und
(ii) einen Prozessor (1002), der dafür konfiguriert ist, durch Auslassen eines oder
mehrerer Übertragungszeitschlitze in einem an den ersten Rahmen angrenzenden zweiten
Rahmen des Uplink-Datenübertragungsmehrfachrahmens das Suchfenster zu verlängern (802),
wobei der an den ersten Rahmen angrenzende zweite Rahmen ferner mindestens einen Empfangszeitschlitz
umfasst;
wobei der Sendeempfänger (1020) ferner dafür konfiguriert ist, im verlängerten Suchfenster
die durch die Nachbar-BTSs (104) übertragenen Synchronisierungskanäle zu empfangen.
25. System nach Anspruch 24, wobei das Mobilkommunikationssystem (100) ein GSM-Netz umfasst.
26. System nach Anspruch 24, wobei der erste Rahmen einen definierten unbelegten Rahmen
im Uplink-Datenübertragungsmehrfachrahmen umfasst und wobei der Prozessor (1002) dafür
konfiguriert ist, durch Auslassen mindestens eines dem definierten unbelegten Rahmen
unmittelbar vorangehenden Übertragungszeitschlitzes im zweiten Rahmen das Suchfenster
zu verlängern.
27. Computerlesbares Medium, das auf diesem gespeicherte Anweisungen enthält, die zum
Aufnehmen einer Synchronisierung einer Mobilstation mit einer oder mehreren Nachbarzellen
(140, 142) in einem Zeitmultiplexvielfachzugriff-Mobilkommunikationssystem (100) durch
ein Computersystem ausführbar sind, wobei das Mobilkommunikationssystem (100) Basissendeempfängerstationen,
BTS, (104), die jeweils eine Zelle (140, 142) definieren, und mindestens eine Mobilstation,
MS, aufweist, die in der Lage ist, mit mindestens einer BTS (104) zu kommunizieren,
wobei die Anweisungen Schritte umsetzen, die Folgendes umfassen:
Verwenden mindestens eines ersten Rahmens als ein Suchfenster in einem Uplink-Datenübertragungsmehrfachrahmen
zum Empfangen von Nachbarzellen-Synchronisierungsinformationen,
Auslassen mindestens eines Übertragungszeitschlitzes in einem an den ersten Rahmen
im Uplink-Datenübertragungsmehrfachrahmen angrenzenden zweiten Rahmen, um das Suchfenster
zu verlängern (802), wobei der an den ersten Rahmen angrenzende zweite Rahmen ferner
mindestens einen Empfangszeitschlitz umfasst; und
Empfangen (804) der Nachbarzellen-Synchronisierungsinformationen im verlängerten Suchfenster.
1. Procédé pour recevoir une synchronisation de station mobile vers une ou plusieurs
cellules voisines (140, 142) dans un système de communication mobile à accès multiples
par division temporelle (100), dans lequel le système de communication mobile (100)
comprend des stations émettrices-réceptrices de base, BTS (104) définissant chacune
une cellule (140, 142) et au moins une station mobile, MS (102) capable de communiquer
avec au moins une BTS (104), lequel procédé consiste à :
utiliser au moins une première trame comme fenêtre de recherche dans une multitrame
de transfert de données en liaison montante pour recevoir des informations de synchronisation
de cellule voisine ;
sauter au moins un créneau temporel de transmission dans une seconde trame adjacente
à la première trame dans la multitrame de transfert de données en liaison montante
pour étendre (802) la fenêtre de recherche, dans lequel la seconde trame adjacente
à la première trame comprend en outre au moins un créneau temporel de réception ;
et
recevoir (804) les informations de synchronisation de cellule voisine dans la fenêtre
de recherche étendue.
2. Procédé selon la revendication 1, dans lequel sauter au moins un créneau temporel
de transmission dans une seconde trame adjacente à la première trame consiste à sauter
au moins un créneau temporel de transmission dans une seconde trame qui précède immédiatement
la première trame.
3. Procédé selon la revendication 2, dans lequel sauter au moins un créneau temporel
de transmission dans une seconde trame qui précède immédiatement la première trame
consiste à sauter au moins un créneau temporel de transmission depuis la seconde trame
qui précède immédiatement et qui est la plus proche de la première trame pour fournir
des créneaux temporels contigus dans la fenêtre de recherche étendue.
4. Procédé selon la revendication 2, consistant en outre à maintenir une limite d'extrémité
de la première trame pour éviter de gêner une trame suivante contiguë à la première
trame.
5. Procédé selon la revendication 1, dans lequel sauter au moins un créneau temporel
de transmission consiste à sauter autant de créneaux temporels de transmission que
nécessaire pour fournir une fenêtre de recherche étendue à une taille permettant de
recevoir toutes les informations de synchronisation de cellule adjacente.
6. Procédé selon la revendication 1, consistant en outre à sauter au moins un créneau
temporel de réception dans une troisième trame adjacente à la première trame et opposée
à la seconde trame dans laquelle ledit au moins un créneau temporel de transmission
a été sauté, afin d'étendre encore la fenêtre de recherche.
7. Procédé selon la revendication 1, dans lequel les informations de synchronisation
de cellule adjacente comprennent une rafale de correction de fréquence, FB associée
à un canal de correction de fréquence, FCCH.
8. Procédé selon la revendication 7, dans lequel les informations de synchronisation
de cellule adjacente comprennent en outre au moins une rafale de synchronisation,
SB associée à un canal de synchronisation, SCH.
9. Procédé selon la revendication 7, consistant en outre à recevoir au moins une rafale
de synchronisation, SB associée à un canal de synchronisation, SCH une fois que le
FCCH a été reçu.
10. Procédé selon la revendication 1, dans lequel utiliser au moins une première trame
comme fenêtre de recherche consiste à utiliser au moins une trame inactive définie
dans la multitrame de transfert de données en liaison montante.
11. Procédé selon la revendication 1, dans lequel utiliser au moins une première trame
comme fenêtre de recherche consiste à utiliser une ou plusieurs quelconques trames
dans la multitrame de transfert de données en liaison montante ayant plusieurs créneaux
temporels disponibles contigus.
12. Procédé selon la revendication 1, dans lequel ladite au moins une station mobile (102)
est associée à une classe multi-créneaux de station mobile qui reçoit moins de créneaux
temporels disponibles consécutifs que disponibles dans la fenêtre de recherche avant
l'extension.
13. Procédé selon la revendication 12, dans lequel sauter au moins un créneau temporel
de transmission consiste à sauter un nombre de créneaux temporels de transmission
nécessaire pour recevoir la classe multi-créneaux de station mobile.
14. Procédé selon la revendication 13, dans lequel sauter un nombre de créneaux temporels
de transmission nécessaire pour recevoir la classe multi-créneaux de station mobile
consiste à sauter un nombre de créneaux temporels de transmission nécessaire pour
fournir dix créneaux temporels consécutifs, comprenant un temps nécessaire pour que
le circuit radiofréquence de la station mobile (102) change entre un canal de transfert
de données et un canal de synchronisation.
15. Procédé selon la revendication 1, consistant en outre à synchroniser au moins partiellement
ladite au moins une station mobile (102) avec une cellule voisine (140, 142) correspondant
aux informations de synchronisation reçues via la fenêtre de recherche étendue.
16. Procédé selon la revendication 1, consistant en outre à répéter une recherche des
informations de synchronisation de cellule adjacente dans plusieurs des premières
trames afin de faciliter la réception des informations de synchronisation de cellule
adjacente dans la fenêtre étendue d'au moins une de la pluralité de premières trames.
17. Procédé selon la revendication 16, dans lequel les informations de synchronisation
comprennent une rafale de correction de fréquence, FB associée à un canal de correction
de fréquence, FCCH, et consistant en outre à déterminer un emplacement d'un canal
de synchronisation, SCH en fonction de l'emplacement du FCCH, et à recevoir le SCH
dans une première trame au moins une multitrame après le FCCH en utilisant un décalage
de synchronisation par rapport à un décalage de synchronisation du FCCH.
18. Procédé selon la revendication 1, dans lequel ladite au moins une station mobile (102)
comprend un type de station mobile où les opérations de transmission et de réception
ne sont pas effectuées simultanément.
19. Procédé selon la revendication 18, dans lequel le type de l'au moins une station mobile
(102) comprend une station mobile de type 1.
20. Appareil fonctionnant dans un réseau sans fil à accès multiple par division dans le
temps (100), comprenant plusieurs cellules (140, 142) chacune définies par une station
émettrice-réceptrice de base, BTS (104), lequel appareil comprend :
un émetteur-récepteur (1020) conçu pour communiquer avec plusieurs BTS (104) voisines
pour recevoir des canaux de synchronisation transmis par les BTS voisines (104) en
utilisant au moins une première trame comme fenêtre de recherche dans une multitrame
de transfert de données en liaison montante ; et
un processeur (1002) conçu pour étendre (802) la fenêtre de recherche en sautant un
ou plusieurs créneaux temporels de transmission dans une seconde trame dans la multitrame
de transfert de données en liaison montante adjacente à la première trame, dans lequel
la seconde trame adjacente à la première trame comprend en outre au moins un créneau
temporel de réception ;
dans lequel l'émetteur-récepteur (1020) est en outre conçu pour recevoir les canaux
de synchronisation transmis par les BTS (104) voisines dans la fenêtre de recherche
étendue.
21. Appareil selon la revendication 20, dans lequel le processeur (1002) comprend un dispositif
de processeur fonctionnant sous la direction d'un ou de plusieurs modules de programme
(1008) comprenant des instructions pour ordonner au dispositif de processeur de sauter
le ou les créneaux temporels de transmission dans la seconde trame adjacente à la
première trame.
22. Appareil selon la revendication 20, dans lequel le processeur (1002) comprend un processeur
de signal numérique, DSP (1006) fonctionnant sous la direction d'un ou de plusieurs
modules de programme comprenant des instructions pour ordonner au DSP (1006) de sauter
le ou les créneaux temporels de transmission dans la seconde trame adjacente à la
première trame.
23. Appareil selon la revendication 20, dans lequel la première trame comprend une trame
inactive définie dans la multitrame de transfert de données en liaison montante, et
dans lequel le processeur (1002) est conçu pour étendre (802) la fenêtre de recherche
en sautant au moins un créneau temporel de transmission dans la seconde trame précédant
immédiatement la trame inactive définie.
24. Système d'accès multiple par division dans le temps, comprenant :
(a) une pluralité de cellules (140, 142) chacune définie par une station émettrice-réceptrice
de base, BTS (104) ;
(b) au moins une station mobile, MS (102) pour communiquer avec plusieurs BTS (104)
voisines de la cellule (140, 142) où ladite au moins une station mobile (102) fonctionne
actuellement, dans lequel chacune des au moins une stations mobiles (102) comprend
:
(i) un émetteur-récepteur (1020) conçu pour communiquer avec les plusieurs BTS (104)
voisines pour recevoir des canaux de synchronisation transmis par les BTS voisines
(104) en utilisant au moins une première trame comme fenêtre de recherche dans une
multitrame de transfert de données en liaison montante ; et
(ii) un processeur (1002) conçu pour étendre (802) la fenêtre de recherche en sautant
un ou plusieurs créneaux temporels de transmission dans une seconde trame dans la
multitrame de transfert de données en liaison montante adjacente à la première trame,
dans lequel la seconde trame adjacente à la première trame comprend en outre au moins
un créneau temporel de réception ;
dans lequel l'émetteur-récepteur (1020) est en outre conçu pour recevoir les canaux
de synchronisation transmis par les BTS (104) voisines dans la fenêtre de recherche
étendue.
25. Système selon la revendication 24, dans lequel le système de communication mobile
(100) comprend un réseau GSM.
26. Système selon la revendication 24, dans lequel la première trame comprend une trame
inactive définie dans la multitrame de transfert de données en liaison montante, et
dans lequel le processeur (1002) est conçu pour étendre la fenêtre de recherche en
sautant au moins un créneau temporel de transmission dans la seconde trame précédant
immédiatement la trame inactive définie.
27. Support lisible par ordinateur sur lequel sont stockées des instructions exécutables
par un système informatique pour recevoir une synchronisation de station mobile vers
une ou plusieurs cellules voisines (140, 142) dans un système de communication mobile
à accès multiples par division temporelle (100), dans lequel le système de communication
mobile (100) comprend des stations émettrices-réceptrices de base, BTS (104) définissant
chacune une cellule (140, 142) et au moins une station mobile, MS capable de communiquer
avec au moins une BTS (104), les étapes d'exécution des instructions consistant à
:
utiliser au moins une première trame comme fenêtre de recherche dans une multitrame
de transfert de données en liaison montante pour recevoir des informations de synchronisation
de cellule voisine ;
sauter au moins un créneau temporel de transmission dans une seconde trame adjacente
à la première trame dans la multitrame de transfert de données en liaison montante
pour étendre (802) la fenêtre de recherche, dans lequel la seconde trame adjacente
à la première trame comprend en outre au moins un créneau temporel de réception ;
et
recevoir (804) les informations de synchronisation de cellule voisine dans la fenêtre
de recherche étendue.